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Abstract:

According to one embodiment, a deviation amount distribution of a
two-dimensional shape parameter between a mask pattern formed on a mask
and a desired mask pattern is acquired as a mask pattern map. Such that a
deviation amount of the two-dimensional shape parameter between a pattern
on substrate formed when the mask is subjected to exposure shot to form a
pattern on a substrate and a desired pattern on substrate fits within a
predetermined range, an exposure is determined for each position in the
exposure shot in forming the pattern on substrate based on the mask
pattern map.

Claims:

1. An exposure determining method comprising: acquiring, as a mask
pattern map, a deviation amount distribution of a two-dimensional shape
parameter between a mask pattern formed on a mask and a desired mask
pattern; and determining, such that a deviation amount of the
two-dimensional shape parameter between a pattern on substrate formed
when the mask is subjected to exposure shot to form a pattern on a
substrate and a desired pattern on substrate fits within a predetermined
range, an exposure for each position in the exposure shot in forming the
pattern on substrate based on the mask pattern map.

2. The exposure determining method according to claim 1, wherein the
two-dimensional shape parameter includes at least one of an area,
peripheral length, dimensions in a longitudinal direction and a lateral
direction, and an aspect ratio of the pattern.

3. The exposure determining method according to claim 1, wherein the mask
pattern map is calculated by a process simulation for calculating a shape
of the mask pattern formed on the mask using mask data of the mask, and
the process simulation is a simulation that takes into account at least
one of a systematic dimension distribution of a mask pattern in the shot
caused in forming the mask pattern and a dimension difference of the mask
pattern depending on density of the mask pattern.

4. The exposure determining method according to claim 1, wherein the
exposure for each position is determined using a correlation between a
shape error of the mask pattern and an exposure for eliminating the shape
error.

5. The exposure determining method according to claim 1, wherein the
exposure for each position is determined using a correlation between a
shape error of the mask pattern and an exposure correction amount for
eliminating the shape error.

6. The exposure determining method according to claim 1, wherein the mask
pattern map is created by measuring the two-dimensional shape parameter
in a plurality of positions in the shot with respect to an actually
formed mask pattern.

7. The exposure determining method comprising: acquiring, as a
pattern-on-substrate map, a deviation amount distribution of a
two-dimensional shape parameter between a pattern on substrate formed
when a mask having a mask pattern is subjected to exposure shot with a
predetermined exposure to form a pattern on a substrate and a desired
pattern on substrate; and determining, such that a deviation amount of
the two-dimensional and the desired pattern on substrate fits within a
predetermined range, an exposure for each position in the exposure shot
in forming the pattern on substrate using the pattern-on-substrate map.

8. The exposure determining method according to claim 7, wherein the
two-dimensional shape parameter includes at least one of an area,
peripheral length, dimensions in a longitudinal direction and a lateral
direction, and an aspect ratio of the pattern.

9. The exposure determining method according to claim 7, further
comprising acquiring, as a mask pattern map, a deviation amount
distribution of the two-dimensional shape parameter between a mask
pattern formed on the mask and a desired mask pattern, wherein the
pattern-on-substrate map is acquired using the mask pattern map.

10. The exposure determining method according to claim 9, wherein the
mask pattern map is calculated by a process simulation for calculating a
shape of the mask pattern formed on the mask using mask data of the mask,
and the process simulation is a simulation that takes into account at
least one of a systematic dimension distribution of a mask pattern in the
shot caused in forming the mask pattern and a dimension difference of the
mask pattern depending on density of the mask pattern.

11. The exposure determining method according to claim 7, wherein the
pattern-on-substrate map is calculated by a process simulation for
calculating a shape of the pattern on substrate using the mask pattern,
and the process simulation is a simulation that takes into account a
systematic dimension distribution of a pattern on substrate in the shot
caused in forming the pattern on substrate.

12. The exposure determining method according to claim 7, wherein the
exposure for each position is determined using a correlation between a
shape error of the pattern on substrate and an exposure for eliminating
the shape error.

13. The exposure determining method according to claim 7, wherein the
exposure for each position is determined using a correlation between a
shape error of the pattern on substrate and an exposure correction amount
for eliminating the shape error.

14. The exposure determining method according to claim 7, wherein the
exposure for each position is determined using a correlation between a
shape of the pattern on substrate and an exposure used in forming the
pattern on substrate.

15. The exposure determining method according to claim 7, wherein the
exposure for each position is determined using a correlation between a
shape of the pattern on substrate and an exposure correction amount used
in forming the pattern on substrate.

16. The exposure determining method according to claim 9, wherein the
mask pattern map is created by measuring the two-dimensional shape
parameter in a plurality of positions in the shot with respect to an
actually formed mask pattern.

17. A method of manufacturing a semiconductor device comprising:
acquiring, as a mask pattern map, a deviation amount distribution of a
two-dimensional shape parameter between a mask pattern formed on a mask
and a desired mask pattern; determining, such that a deviation amount of
the two-dimensional shape parameter between a pattern on substrate formed
when the mask is subjected to exposure shot to form a pattern on a
substrate and a desired pattern on substrate fits within a predetermined
range, an exposure for each position in the exposure shot in forming the
pattern on substrate based on the mask pattern map; and exposing the mask
based on the determined exposure to form a pattern on the substrate.

18. The method of manufacturing a semiconductor device according to claim
17, wherein the two-dimensional shape parameter includes at least one of
an area, peripheral length, dimensions in a longitudinal direction and a
lateral direction, and an aspect ratio of the pattern.

19. The method of manufacturing a semiconductor device according to claim
17, wherein the mask pattern map is calculated by a process simulation
for calculating a shape of the mask pattern formed on the mask using mask
data of the mask, and the process simulation is a simulation that takes
into account at least one of a systematic dimension distribution of a
mask pattern in the shot caused in forming the mask pattern and a
dimension difference of the mask pattern depending on density of the mask
pattern.

20. A computer program product executable by a computer and having a
computer-readable recording medium including a plurality of commands for
determining an exposure, the commands causing the computer to execute:
acquiring, as a mask pattern map, a deviation amount distribution of a
two-dimensional shape parameter between a mask pattern formed on a mask
and a desired mask pattern; and determining, such that a deviation amount
of the two-dimensional shape parameter between a pattern on substrate
formed when the mask is subjected to exposure shot to form a pattern on a
substrate and a desired pattern on substrate fits within a predetermined
range, an exposure for each position in the exposure shot in forming the
pattern on substrate based on the mask pattern map.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priority
from the prior Japanese Patent Application No. 2010-007507, filed on Jan.
15, 2010; the entire contents of which are incorporated herein by
reference.

FIELD

[0002] Embodiments described herein relate generally to an exposure
determining method, a method of manufacturing a semiconductor device, and
a computer program product.

BACKGROUND

[0003] The progress of semiconductor manufacturing technologies in recent
years is extremely remarkable. Semiconductor integrated circuit devices
(semiconductor devices) having a minimum processing dimension of 50
nanometer are mass-produced. Such microminiaturization of semiconductor
devices is realized by the remarkable progress of a lithography
technology using a photomask or the like. For example, in a lithography
process, when a pattern dimension of the photomask fluctuates, because
dimension accuracy of a resist pattern formed on a substrate is
deteriorated, dimensions of patterns formed on the substrate are
non-uniform in an exposure shot. Therefore, it is necessary to
sufficiently suppress a fluctuation amount (an error) of the pattern
dimension of the photomask. However, a mask dimension error of the
photomask inevitably occurs in manufacturing of the photomask.

[0004] It is demanded to form a desired pattern on substrate even if the
pattern dimension of the photomask fluctuates.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a diagram for explaining a concept of an exposure
determining method according to a first embodiment;

[0006]FIG. 2 is a block diagram of the configuration of an exposure-map
creating apparatus according to the first embodiment;

[0007]FIG. 3 is a flowchart for explaining an exposure processing
procedure according to the first embodiment;

[0008]FIG. 4 is a diagram for explaining a relation between a
pattern-on-wafer map and an exposure map;

[0009]FIG. 5 is a diagram for explaining a correlation between an error
of a mask pattern shape and an optimum exposure correction amount;

[0010]FIG. 6 is a diagram for explaining problems that occur when a
target is corrected based on a dimension only in one direction;

[0011]FIG. 7 is a diagram for explaining processing for setting an
exposure correction amount corresponding to a mask pattern shape;

[0012]FIG. 8 is a flowchart for explaining an exposure processing
procedure according to a second embodiment;

[0013]FIG. 9 is a diagram of a hardware configuration of an exposure-map
creating apparatus; and

[0014] FIG. 10 is a block diagram of the configuration of an exposure
apparatus.

DETAILED DESCRIPTION

[0015] In general, according to one embodiment, a deviation amount
distribution of a two-dimensional shape parameter between a mask pattern
formed on a mask and a desired mask pattern is acquired as a mask pattern
map. Such that a deviation amount of the two-dimensional shape parameter
between a pattern on substrate formed when the mask is subjected to
exposure shot to form a pattern on a substrate and a desired pattern on
substrate fits within a predetermined range, an exposure is determined
for each position in the exposure shot in forming the pattern on
substrate based on the mask pattern map.

[0016] Exemplary embodiments of an exposure determining method, a method
of manufacturing a semiconductor device, and a computer program product
will be explained below in detail with reference to the accompanying
drawings. The present invention is not limited to the following
embodiments.

[0017] In a first embodiment, a plane shape (a dimension, size, an area,
etc.) of a mask pattern of a mask (a photomask) is acquired by an
experiment or a calculation and a pattern shape of a pattern to be formed
on a substrate such as a wafer is predicted based on an acquisition
result. An exposure map for correcting a deviation amount between the
pattern shape of the pattern predicted to be formed on the wafer and a
target shape (an exposure correction amount distribution in a shot for
correcting an exposure) is created. After the exposure map is created,
exposure on the wafer is performed using the created exposure map,
whereby a pattern having a desired pattern shape (a two-dimensional shape
parameter) is formed on the wafer. In the exposure map, a map of
exposures (a distribution of dosages) is specified within an exposure
shot such that dimensions of patterns formed on the wafer are
uniformalized in an exposure shot.

[0018] For example, when a contact hole pattern is formed on the wafer, an
exposure of an exposure apparatus is changed in a shot or between shots
such that an area of a contact hole transferred onto the wafer by
exposure processing is equal to a desired area. In the following
explanation, the contact hole pattern is formed on the wafer. However, a
pattern formed on the wafer can be a pattern other than the contact hole
pattern such as a line pattern.

[0019]FIG. 1 is a diagram for explaining a concept of an exposure
determining method (an exposure correcting method) according to the
embodiment. First, design data D1 of a pattern (a post-etching pattern)
to be formed on a wafer is created by a computer such as a design-data
creating apparatus (S1).

[0020] Thereafter, a lithography target is created using the design data
D1. A proximity correction apparatus 10 such as an OPC apparatus or a PPC
apparatus creates mask data D2 by applying optical proximity correction
(OPC) or process proximity correction (PPC) to the lithography target
(S2).

[0021] In a mask manufacturing process P1, a mask having a mask pattern
corresponding to the mask data D2 is manufactured. In other words, in the
mask manufacturing process P1, a mask having a mask pattern formed in a
pattern shape substantially the same as a pattern shape of the mask data
D2 is manufactured. In the mask manufacturing process P1, a rendering
apparatus 51, an applying and developing apparatus 52, a processing
apparatus 53, a cleaning apparatus 54, and the like are used.

[0022] The rendering apparatus 51 is an apparatus that applies EB
rendering to a resist on a mask substrate. The applying and developing
apparatus 52 is an apparatus having a function of applying the resist for
the EB rendering on the mask substrate before the EB rendering on the
mask substrate is performed and a function of developing the resist on
the mask after the EB rendering and forming a resist pattern on the mask.
The processing apparatus 53 is an apparatus that performs base film
processing such as etching from above the resist pattern on the mask and
forms a mask pattern such as a contact hole on the mask. The cleaning
apparatus 54 is an apparatus that cleans the mask on which the mask
pattern is formed. The cleaning apparatus 54 can clean the mask
immediately after the mask pattern is formed on the mask or can clean the
mask when the mask is stained after exposure processing is performed
using the mask.

[0023] The mask pattern on the mask manufactured in the mask manufacturing
process P1 roughly includes two regions of a light transmitting section
and a light blocking section (a semi-transmitting section). The
dimension, the peripheral length, the shape, the area, the transmittance,
the phase, and the like of the mask pattern are evaluation values that
characterize a mask pattern shape. Ideally, it is desirable that a mask
having a pattern shape same as the mask data D2 is formed. However,
through a process of mask rendering, resist development after the mask
rendering, and base film processing with a resist pattern used as a mask
material (hereinafter, "mask process"), the evaluation values have a
systematic distribution in a mask surface. When the mask having the
systematic distribution is exposed with a fixed exposure, the systematic
distribution on the mask is directly reflected on a pattern shape on the
wafer. As a result, the pattern shape on the wafer changes according to
the systematic distribution on the mask of the evaluation values
(hereinafter, "evaluation value systematic distribution"). It is likely
that deterioration in device characteristics is caused according to the
pattern shape change.

[0024] Therefore, development of a mask process for minimizing the
systematic distribution of the evaluation values on the mask is
necessary. However, enormous cost and time are required for the
development of the mask process. In this embodiment, an exposure map
system that can change an exposure in a shot during exposure on the wafer
is used.

[0025] To apply exposure to the wafer using the exposure map system,
evaluation values on a manufactured mask are calculated by an experiment
or a calculation. Specifically, after the mask data D2 is created, a mask
pattern shape D3 is derived as shape data of a mask pattern (evaluation
values of the mask pattern) formed on the mask.

[0026] A mask-pattern-shape calculating apparatus 20 can acquire the mask
pattern shape D3 according to a mask manufacturing simulation.
Alternatively, the mask pattern shape D3 can be acquired by an actual
mask manufacturing experiment. The mask-pattern-shape calculating
apparatus 20 is a computer that predicts a plane shape of a mask pattern
using the mask data D''. The mask-pattern-shape calculating apparatus 20
calculates the mask pattern shape D3 based on a process condition or the
like in the mask manufacturing process P1. The mask-pattern-shape
calculating apparatus 20 calculates the mask pattern shape D3 using, for
example, a calculation model for calculating the mask pattern shape D3
(S3). Specifically, the mask-pattern-shape calculating apparatus 20
models the evaluation value systematic distribution in the mask surface
and further models a dimension conversion error based on a density
difference of the mask pattern. The mask-pattern-shape calculating
apparatus 20 applies the models to the mask data 2D to reproduce the
evaluation value systematic distribution in the mask surface.

[0027] For example, the mask-pattern-shape calculating apparatus 20
calculates the mask pattern shape D3 according to a process simulation
taking into account at least one of a systematic dimension distribution
of the mask pattern caused when the mask pattern is formed and a
dimension difference of the mask pattern depending on the density of the
mask pattern.

[0028] The evaluation value systematic distribution of the mask pattern is
often a distribution such as concentric circles or a tilt in the entire
mask surface. Therefore, the evaluation value systematic distribution can
be accurately reproduced by a combination of a surface formula and a
polynomial. The density difference of the mask pattern has a correlation
with a dimension value obtained by subjecting the influence from a near
pattern to convolutional integration with Gaussian and an opening angle
to an adjacent pattern. Therefore, the evaluation value systematic
distribution can be accurately reproduced by a model using a function
system of the dimension value and the opening angle.

[0029] On the other hand, when the mask pattern shape D3 is derived by an
experiment, a mask is manufactured in the mask manufacturing process P1.
Concerning the mask manufactured in the mask manufacturing process P1,
various positions where evaluation values such as shape should be
measured on the mask (mask patterns as measurement targets) are selected.
Evaluation values of the selected mask patterns are measured by a
scanning electron microscope (SEM), an optical measurement apparatus, an
image acquiring apparatus, or the like. A diameter in a longitudinal
direction, a diameter in a lateral direction, and the like of a contact
hole are measured as a pattern shape of a contact hole pattern.

[0030] In this embodiment, two-dimensional shape parameters of the mask
pattern are derived as the mask pattern shape D3. The two-dimensional
shape parameters of the mask pattern are elements for determining a
two-dimensional shape of the mask pattern viewed from a principal plane
side of the mask and are, for example, an area, peripheral length,
dimensions in the longitudinal direction and the lateral direction, and
an aspect ratio.

[0031] After the mask pattern shape D3 in the mask surface is derived by
the simulation or the experiment, an imaginary pattern shape (dimension)
and an imaginary shape distribution on the wafer exposed with the same
exposure in a shot on this mask are calculated.

[0032] Specifically, after the mask pattern shape D3 is derived, a
mask-pattern-map creating apparatus 25 creates a mask pattern map m1
explained later (S4). The mask-pattern-map creating apparatus 25 is a
computer that creates the mask pattern map m1 using the mask pattern
shape D3. The mask pattern map m1 is a map (a distribution in shot)
concerning the shapes of mask patterns in various positions in an
exposure shot as an exposure target on the wafer. In the mask pattern map
m1, information concerning a shape difference between the shape of the
mask pattern formed on the mask in the mask manufacturing process P1 and
the shape of an ideal mask pattern formed when a manufacturing error does
not occur in mask manufacturing is stored.

[0033] After the mask pattern map m1 is created, an optical simulation is
carried out using the mask pattern map m1 and a processing simulation is
carried out to calculate an imaginary shape distribution (a shape
distribution of a pattern after processing) on the wafer. The imaginary
shape distribution (resist shape distribution) on the wafer can be
calculated by only the optical simulation using the mask pattern map m1.

[0035] The pattern-on-wafer map m2 is a map (a distribution in shot)
concerning plane shapes of patterns on wafer (resist patterns or
post-etching patterns) in various positions in a shot. In the
pattern-on-wafer map m2, information concerning a shape difference
between the shape of a pattern on wafer formed on the wafer in the
pattern forming process P2 and an ideal shape (a target shape, for
example, a design layout) of a pattern on wafer formed when a formation
error does not occur in the pattern on wafer formation is stored.

[0036] The pattern-on-wafer-map calculating apparatus 30 creates the
pattern-on-wafer map m2 using, for example, a calculation model for
calculating the pattern-on-wafer map m2. The calculation model for
calculating the pattern-on-wafer map m2 is a model for converting the
mask pattern map m1 into the pattern-on-wafer map m2 using, for example,
a correspondence relation between an error (a deviation amount from an
ideal value) of a pattern shape in the mask pattern map m1 and a pattern
shape error of the pattern on wafer.

[0037] In the pattern forming process P2, a pattern on wafer (a resist
pattern or a post-etching pattern) is formed on the wafer using the mask
manufactured in the mask manufacturing process P1. In the pattern forming
process P2, an exposure apparatus 60, an applying and developing
apparatus 56, a processing apparatus 57, and the like are used.

[0038] The exposure apparatus 60 is an apparatus that performs exposure
using the mask manufactured in the mask manufacturing process P1 to
thereby transfer a mask pattern onto the wafer. The exposure apparatus 60
irradiates light emitted from a secondary light source on a mask and
projects an image of a pattern formed on a mask onto the wafer via a
projection optical system to expose the wafer.

[0039] The applying and developing apparatus 56 is an apparatus having
functions same as those of the applying and developing apparatus 52. The
applying and developing apparatus 56 has a function of applying a resist
on the wafer before exposure processing by the exposure apparatus 60 is
performed and a function of developing the resist on the exposed wafer
and forming a resist pattern on the wafer. The processing apparatus 57 is
an apparatus having functions same as those of the processing apparatus
53. The processing apparatus 57 performs base film processing such as
etching from above the resist pattern on the wafer and forms a pattern
such as a contact hole on the wafer.

[0040] In this way, in the pattern forming process P2, the exposure
processing to the wafer is performed by the exposure apparatus 60.
Therefore, when the exposure apparatus 60 is known in advance, the mask
pattern map m2 can be calculated by an optical simulation taking into
account a machine difference of the exposure apparatus 60. For example,
at least one of optical parameters of the exposure apparatus 60 affecting
a pattern on wafer shape such as an illumination shape, an illumination
luminance distribution, the size of a lens, a degree of polarization,
lens aberration, lens transmittance, polarization aberration, an
exposure, focus offset, parallelism of scan of the mask and the wafer, a
distribution of exposure wavelength, and a projection lens NA is
incorporated into the optical simulation.

[0041] By incorporating the optical parameter in this way, it is possible
to calculate an imaginary shape distribution into which not only an
evaluation value systematic distribution on the mask but also an
evaluation value systematic distribution due to the optical parameter of
the exposure apparatus 60 is incorporated. This makes it possible to
simultaneously correct shape errors indicated by the evaluation value
systematic distributions due to both the mask and the exposure apparatus
60. Further, by carrying out the processing simulation, it is possible to
correct shape errors indicated by evaluation value systematic
distributions due to not only lithography but also a processing process.

[0042] The pattern-on-wafer map m2 can be calculated by a formation
experiment of a pattern on wafer. In this case, the pattern on wafer is
formed on the wafer in the pattern forming process P2. Pattern shapes in
various positions (patterns on wafer as measurement targets) of the
pattern on wafer formed in the pattern forming process P2 are measured by
a SEM or the like. The pattern-on-wafer map m2 is a map (a distribution)
of dimensions concerning pattern shapes on the wafer in various positions
in a shot.

[0043] After the pattern-on-wafer map m2 is calculated, an exposure-map
creating apparatus 40 creates an exposure map m3. The exposure-map
creating apparatus 40 calculates the exposure map m3 for forming a
pattern having a desired pattern shape on the wafer using the
pattern-on-wafer map m2 (S6).

[0044] In other words, in this embodiment, a shape difference between an
imaginary shape distribution on the wafer and a target shape is
calculated in a shot in advance and a correction map of exposures is
created such that the shape difference is smaller than a predetermined
value. To correct the shape difference, a dimension fluctuation amount
with respect to unit exposure fluctuation is specified in advance.

[0045] To form a pattern on wafer having a desired pattern shape, it is
necessary to expose, in various positions in the shot, a resist on the
wafer with an exposure corresponding to the positions (the
pattern-on-wafer map 2). Therefore, the exposure map m3 is a map (a
distribution in shot) of exposures (dosages) in the various positions in
the shot. The exposure map m3 can be a map of exposure correction amounts
in the various positions in the shot. After the exposure map m3 is
created, the exposure map m3 is applied to the pattern forming process P2
and pattern formation is performed on the wafer.

[0046] For example, in the mask manufacturing process P1, in a process for
manufacturing a mask, a pattern shape of a mask pattern formed on the
mask deviates from a desired pattern shape. In the pattern forming
process P2, a pattern shape of a pattern formed on the wafer deviates
from a desired pattern shape because of systematic illumination shape
deviation, illumination unevenness, aberration fluctuation, phase
fluctuation of a lens, transmittance fluctuation, and the like in the
shot caused by the illumination and the lens of the exposure apparatus
60. The pattern shape of the pattern formed on the wafer also deviates
from the desired pattern shape because of systematic dimension
fluctuation, phase fluctuation, transmittance fluctuation, and the like
in the mask used in the exposure. The pattern shape of the pattern formed
on the wafer also deviates from the desired pattern shape because of
systematic fluctuation caused in the processing process.

[0047] In this embodiment, the exposure map m3 for correcting a deviation
amount between the pattern-on-wafer map m2 and the target pattern shape
of the pattern on wafer is created. Therefore, it is possible to correct,
using the exposure map m3, a systematic dimension error in the shot on
the wafer caused because of the mask manufacturing process P1 and the
pattern forming process P2. Specifically, it is possible to correct,
through exposure correction, dimension fluctuation on the wafer due to a
mask dimension, shape, phase, transmittance, systematic optical parameter
fluctuation in the shot of the exposure apparatus 60, systematic
fluctuation in the shot caused in the processing process, and the like.
The exposure map m3 can be a map of exposure correction amounts for
correcting a deviation amount between the mask pattern map m1 and the
target pattern shape of the pattern on wafer.

[0048] When a mask pattern is formed by uniformalized patterns (periodic
patterns having the same shape) as in a memory product, a dimension
change amount with respect to fluctuation in a unit exposure is
substantially a fixed value. Therefore, when the mask pattern is the
memory product, it is relatively easy to calculate a correction amount of
an exposure for correcting a shape difference. However, in a system LSI
product or the like, because mask patterns having various kinds of shapes
are formed on the same mask, a dimension change amount with respect to
fluctuation in a unit exposure is different for each of the mask
patterns.

[0049] In such a case, it is possible to divide a mask surface into meshes
of about several micrometers to several hundred micrometers and calculate
an exposure correction amount for minimizing a deviation amount from an
ideal value of a pattern on wafer in the meshes. Even when an exposure
and a focus deviate, an exposure correction amount for minimizing a shape
difference with respect to a target dimension (an exposure correction
amount with large exposure margin) can be calculated. After the exposure
correction amount is calculated for each of the divided meshes, exposure
correction amounts of the meshes are joined to create the exposure map m3
in the mask surface.

[0050]FIG. 2 is a block diagram of the configuration of the exposure-map
creating apparatus according to the embodiment. The exposure-map creating
apparatus (an exposure determining apparatus) 40 includes an input unit
41, a pattern-map storing unit 42, a correlation storing unit 43, an
exposure-map creating unit 45, and an output unit 46.

[0051] The input unit 41 receives input of the pattern-on-wafer map m2
from the pattern-on-wafer-map calculating apparatus 30 or the like. The
input unit 41 receives input of correlation information indicating a
correlation between an exposure correction amount (an optimum exposure
correction amount B explained later) and an error amount (a plane shape
difference D explained later) of a pattern shape (an area, etc.) on the
wafer. The plane shape difference D is information indicating a
difference concerning a shape between a pattern shape on the wafer
calculated by a simulation or the like and a target shape of a pattern on
wafer formed on the wafer. The correlation information is a mask error
enhancement factor (MEF) (a ratio of a dimension fluctuation amount of
the pattern on wafer with respect to a dimension fluctuation amount of
the mask) concerning the area of a contact hole. The input unit 41 sends
the pattern-on-wafer map m2 to the pattern-map storing unit 42 and sends
the correlation information to the correlation storing unit 43.

[0052] The correlation information can be a correlation between the
pattern shape on the wafer and a wafer exposure. The correlation
information can also be a correlation between the plane shape difference
D and the wafer exposure or can be a correlation between the pattern
shape on the wafer and the optimum exposure correction amount B. The
pattern-map storing unit 42 is a memory or the like that stores the
pattern-on-wafer map m2. The correlation storing unit 43 is a memory or
the like that stores the correlation information.

[0053] The exposure-map creating unit 45 creates the exposure map m3 using
the pattern-on-wafer map m2 and the correlation information. The exposure
map m3 is distribution information concerning an exposure in a shot in
forming a pattern on wafer using the mask. For example, when the pattern
on wafer calculated by a simulation or the like is larger than the target
pattern in the plane shape difference D, the exposure is increased to
reduce the pattern on wafer. When the pattern on wafer calculated by a
simulation or the like is smaller than the target pattern, the exposure
is reduced to increase the pattern on wafer.

[0054] The output unit 46 outputs the exposure map m3 created by the
exposure-map creating unit 45. The exposure map m3 output from the output
unit 46 is input to the exposure apparatus 60 and used in exposure
processing to the wafer.

[0055] An exposure processing procedure according to the embodiment is
explained. FIG. 3 is a flowchart for explaining the exposure processing
procedure according to the first embodiment. First, the plane shape
difference D as a shape difference between the pattern shape on the wafer
calculated by a simulation or the like and the target shape of a pattern
formed on the wafer is calculated for various patterns on wafers in
advance. Further, an optimum exposure correction amount (the optimum
exposure correction amount B) necessary for forming the patterns on wafer
is calculated in advance. The plane shape difference D and the optimum
exposure correction amount B can be calculated by a simulation or can be
calculated by an experiment. Further, a correlation between the plane
shape difference D and the optimum exposure correction amount B is
derived as correlation information in advance (step S10). The correlation
information is stored in the correlation storing unit 43.

[0057] The exposure-map creating unit 45 of the exposure-map creating
apparatus 40 creates the exposure map m3 based on the correlation
information in the correlation storing unit 43 and the pattern-on-wafer
map m2 in the pattern-map storing unit 42 (step S30).

[0058]FIG. 4 is a diagram for explaining a relation between the
pattern-on-wafer map m2 and the exposure map m3. The pattern-on-wafer map
m2 is a distribution in shot of shape errors of patterns on wafer. The
exposure map m3 is a distribution in shot of the optimum exposure
correction amount B. In FIG. 4, the distribution in shot of the
pattern-on-wafer map m2 is regions a1 to a4 divided for each magnitude of
the shape errors of the patterns on wafer. The distribution in shot of
the exposure map m3 is regions b1 to b4 divided for each magnitude of the
optimum exposure correction amount B. Because the pattern-on-wafer map m2
and the exposure map m3 have the correlation, the distribution in shot of
the regions a1 to a4 and the distribution in shot of the regions b1 to b4
have substantially the same distributions.

[0059] The output unit 46 outputs the exposure map m3 created by the
exposure-map creating unit 45. The exposure map m3 output from the output
unit 46 is set in the exposure apparatus 60 and the exposure processing
to the wafer is performed according to the exposure map m3 (step S40).
This makes it possible to perform the exposure processing to the wafer
with the optimum exposure correction amount B corresponding to the plane
shape difference D, which is the shape error amount of the patterns on
wafer.

[0060] As explained above, in this embodiment, contact hole patterns or
the like are formed such that, rather than dimensions (CD),
two-dimensional shape parameters such as an area, peripheral length,
dimensions in the longitudinal direction and the lateral direction, and
an aspect ratio are uniformalized on the wafer. Consequently, electric
characteristics of the contact hole patterns uniformly approach a target
value in a plane. Therefore, performance of a semiconductor device is
stabilized and occurrence of defective products can be suppressed.

[0061] In this embodiment, the exposure map m3 is created based on the
correlation between the plane shape difference D and the optimum exposure
correction amount B. However, the exposure map m3 can be created based on
a correlation between the plane shape difference D and the optimum
exposure.

[0062] In this embodiment, the pattern-on-wafer map m2 is derived using
the mask pattern map m1. However, when the pattern-on-wafer map m2 is
derived by an experiment, the creation of the mask pattern map m1 can be
omitted. In this case, for example, a correction amount of an exposure
with respect to an exposure (which can be non-uniform) used in deriving
the pattern-on-wafer map m2 is calculated.

[0063] As explained above, according to the first embodiment, an exposure
correction amount and an exposure in a shot are determined based on the
two-dimensional pattern shape stored in the pattern-on-wafer map m2.
Therefore, it is possible to accurately determine an exposure correction
amount and an exposure for enabling formation of a pattern having a
desired two-dimensional shape parameter on the wafer.

[0064] A second embodiment of the present invention is explained with
reference to FIGS. 5 to 8. In the second embodiment, an exposure
correction amount is set based on an error of a mask pattern shape (the
mask pattern map m1). In the following explanation, the exposure map m3
is derived using a correlation between the error of the mask pattern
shape and an optimum exposure correction amount. However, the exposure
map m3 can be derived using a correlation between the error of the mask
pattern shape and an optimum exposure.

[0065]FIG. 5 is a diagram for explaining the correlation between the
error of the mask pattern shape and the optimum exposure correction
amount. Pattern dimensions in an x direction of contact holes h1 to h4 on
the design data D1 are A to D, respectively, and pattern dimensions in a
y direction are A' to D', respectively. Contact hole patterns are formed
on a wafer using the contact holes h1 to h4, whereby not-shown contact
hole patterns H1 to H4 are respectively formed as patterns on wafer
corresponding to the shapes of the contact holes h1 to h4. At this point,
a distribution of shape deviations occurs in a shot.

[0066] In FIG. 5, a correspondence relation between an error of a mask
pattern shape and the optimum exposure correction amount B is shown. The
correspondence relation is obtained when adjustment of an exposure is
applied to a plurality of patterns having different mask pattern
diameters such that the resist pattern diameters respectively have
desired values. The correspondence relation between the error of the mask
pattern shape and the optimum exposure correction amount B can be
calculated by an experiment or can be calculated by an imaging simulation
using the mask pattern shape.

[0067] On the upper left side of FIG. 5, a correspondence relation between
dimension deviation amounts (contact dimension deviation amounts) in the
x direction of the contact hole patterns H1 to H4 from a desired
dimension and the optimum exposure correction amount B is shown. On the
upper right side of FIG. 5, a correspondence relation between area
deviation amounts (contact area deviation amounts) of the contact hole
patterns H1 to H4 from a desired area is shown.

[0068] On the lower left side, the contact holes h1 to h4 and the order of
magnitudes of contact dimension deviation amounts of the contact hole
patterns H1 to H4 are shown in association with each other. On the lower
right side of FIG. 5, the contact holes h1 to h4 and the order of
magnitudes of contact area deviation amounts of the contact hole patterns
H1 to H4 are shown in association with each other.

[0069] When a mask pattern shape is a contact hole, as shown on the left
side of FIG. 5, there is no correlation between contact dimension
deviation amounts in one direction (e.g., the x direction) of the contact
holes H1 to H4 and the optimum exposure correction amount B. For example,
even when the order of magnitudes of the contact dimension deviation
amounts of the contact hole patterns H1 to H4 is the contact hole h4, the
contact hole h3, the contact hole h2, and the contact hole h1, the
magnitudes of the optimum exposure correction amount B are not always in
this order.

[0070]FIG. 6 is a diagram for explaining problems that occur when a
target is corrected based on a dimension only in one direction. As shown
in (a) of FIG. 6, when the exposure processing is applied, with a
standard exposure (a proper exposure without correction), to an ideal
mask pattern Mp1 without a manufacturing error or the like, a resist
pattern R1 corresponding to a desired dimension target is formed.

[0071] On the other hand, as shown in (b) of FIG. 6, when the exposure
processing is applied to a mask pattern Mp2 having a dimension error with
the standard exposure, a resist pattern R2 with a shape deviating due to
the dimension error is formed. For example, when the mask pattern Mp2 is
enlarged in the lateral direction because of a manufacturing error or the
like, the resist pattern R2 is also formed to be enlarged in the lateral
direction. In such a case, if an exposure is corrected such that a
dimension in the lateral direction is equal to a desired dimension
target, a resist pattern R3 after the exposure correction is small in a
dimension in the longitudinal direction. Therefore, if a resist pattern
is formed on a substrate using such an exposure correction amount, the
resist pattern is formed at a desired dimension only in the lateral
direction and cannot be formed at the desired dimension in the
longitudinal direction. This is because the optimum exposure correction
amount B necessary in forming a resist pattern of a contact hole on the
wafer is a value corresponding to the shape of a contact hole pattern to
be formed and is not a value corresponding to only a dimension in the x
direction of the contact hole pattern to be formed. Therefore, even if a
wafer exposure correction amount is set based on the direction in the x
direction of a pattern on wafer and a target dimension in the x
direction, a desired pattern on wafer cannot be formed.

[0072] In this way, when the mask pattern has an anisotropic dimension
error, if the diameter of the resist pattern of the contact hole is
adjusted to the target dimension by adjusting the exposure correction
amount, the area of the contact hole pattern deviates from a target area.
In the semiconductor device, the contact hole pattern plays a role of
electrically connecting wires of an upper layer and a lower layer.
Therefore, if the sectional area of the contact hole pattern deviates
from the target area, the electric resistance of the contact hole pattern
also deviates. As a result, the operation characteristic of the
semiconductor device is adversely affected.

[0073] As shown on the upper right side of FIG. 5, there is a correlation
between contact area deviation amounts of the contact hole patterns H1 to
H4 and the optimum exposure correction amount B. For example, when the
order of the magnitudes of the contact area deviation amounts of the
contact holes h1 to h4 is the contact hole h3 (an area is C×C'),
the contact hole h4 (an area is D×D'), the contact hole h1 (an area
is A×A'), and the contact hole h2 (an area is B×B'), the
magnitudes of the optimum exposure correction amount B is also in this
order. Therefore, by setting the optimum exposure correction amount B
based on a deviation amount of a two-dimensional shape (an area, etc.) of
the mask pattern, it is possible to form a pattern having a desired shape
on the wafer. In this way, in this embodiment, the contact hole patterns
or the like are formed such that, rather than dimensions (CD), areas and
the like are uniformalized on the wafer. Consequently, electric
characteristics of the contact hole patterns uniformly approach a target
value in a plane. Therefore, performance of the semiconductor device is
stabilized and occurrence of defective products can be suppressed.

[0074]FIG. 7 is a diagram for explaining setting processing for an
exposure correction amount corresponding to a mask pattern shape. Mask
patterns (contact hole patterns) having various shape errors
corresponding to the mask manufacturing process P1 are formed in a mask
M. Because, for example, contact hole patterns formed in positions p1 to
p3 in the mask M cause various shape errors according to the mask
manufacturing process P1, contact areas on the mask M of the contact hole
patterns also cause various errors. Therefore, the exposure-map creating
apparatus 40 (the exposure determining apparatus) sets, to eliminate the
errors of the contact areas, an exposure correction amount for each of
the positions p1 to p3 to thereby create the exposure map m3.

[0075] An exposure processing procedure according to the second embodiment
is explained below. FIG. 8 is a flowchart for explaining the exposure
processing procedure according to the second embodiment. In the
processing procedure shown in FIG. 8, redundant explanation of processing
same as the processing procedure shown in FIG. 3 is omitted.

[0076] First, a correlation between a contact area deviation amount on a
mask calculated by a simulation, an experiment, or the like and the
optimum exposure correction amount B is derived as correlation
information in advance (step S10). The correlation information is derived
by repeating the simulation and the experiment to calculate an optimum
exposure in advance and setting a correlation between the contact area
deviation amount and the optimum exposure as a rule or a model function.
Specifically, a shape difference between a pattern shape on the mask
calculated by the simulation, the experiment, or the like, a target shape
of a pattern formed on the wafer is calculated for various patterns on
mask in advance. Further, an optimum exposure correction amount necessary
for forming patterns on wafer (the optimum exposure correction amount B)
is calculated in advance. A correlation between the shape difference and
the optimum exposure correction amount B is derived as correlation
information. The correlation information is stored in the correlation
storing unit 43.

[0077] After the correlation information between the contact area
deviation amount and the optimum exposure correction amount B is derived,
the mask-pattern-map creating apparatus 25 creates the mask pattern map
m1 using the mask pattern shape D3 (step S120). The created mask pattern
map m1 is stored in the pattern-map storing unit 42.

[0078] The exposure-map creating unit 45 of the exposure-map creating
apparatus 40 creates the exposure map m3 based on the correlation
information in the correlation storing unit 43 and the mask pattern map
m1 in the pattern-map storing unit 42 (step S130).

[0079] The output unit 46 outputs the exposure map m3 created by the
exposure-map creating unit 45. The exposure map m3 output from the output
unit 46 is set in the exposure apparatus 60 and exposure processing to
the wafer is performed according to the exposure map m3 (step S140). This
makes it possible to perform the exposure processing to the wafer with
the optimum exposure correction amount B corresponding to the contact
area deviation amount, which is an error amount of the mask pattern
shape.

[0080] Adjustment of the exposure correction amount using the exposure map
m3 is performed, for example, for each layer or for each mask in a wafer
process. A semiconductor device (a semiconductor integrated circuit) is
manufactured using the exposure map m3 corresponding to each layer or
each mask. Specifically, the exposure map m3 is created for each layer or
each mask in the wafer process. The exposure processing is performed
using the exposure map m3 and, thereafter, development processing,
etching processing, and the like for the wafer are performed. When the
semiconductor device is manufactured, the creation processing for the
exposure map m3, the exposure processing, the development processing, the
etching processing, and the like are repeated for each layer.

[0081] A hardware configuration of the exposure-map creating apparatus 40
is explained below. FIG. 9 is a diagram of a hardware configuration of
the exposure-map creating apparatus. The exposure-map creating apparatus
40 includes a central processing unit (CPU) 91, a read only memory (ROM)
92, a random access memory (RAM) 93, a display unit 94, and an input unit
95. In the exposure-map creating apparatus 40, the CPU 91, the ROM 92,
the RAM 93, the display unit 94, and the input unit 95 are connected via
a bus line.

[0082] The CPU 91 creates the exposure map m3 using an exposure-map
creating program (an exposure determining program) 97, which is a
computer program for creating the exposure map m3. The display unit 94 is
a display device such as a liquid crystal monitor. The display unit 94
displays, based on an instruction from the CPU 91, the pattern-on-wafer
map m2, a correlation between the optimum exposure correction amount B
and the plane shape difference D, a correlation between the contact area
deviation amount and the optimum exposure correction amount B, the
exposure map m3, and the like. The input unit 95 includes a mouse and a
keyboard. The input unit 95 receives input of instruction information
(parameters necessary for creation of an exposure map, etc.) externally
input from a user. The instruction information input to the input unit 95
is sent to the CPU 91.

[0083] The exposure-map creating program 97 is stored in the ROM 92 and
loaded into the RAM 93 via the bus line. In FIG. 9, a state in which the
exposure-map creating program 97 is loaded into the RAM 93 is shown.

[0084] The CPU 91 executes the exposure-map creating program 97 loaded
into the RAM 93. Specifically, in the exposure-map creating apparatus 40,
according to an instruction input from the input unit 95 by the user, the
CPU 91 reads out the exposure-map creating program 97 from the ROM 92,
expands the exposure-map creating program 97 in a program storage region
in the RAM 93, and executes various kinds of processing. The CPU 91
causes a data storage region formed in the RAM 93 to temporarily store
various data generated in the various kinds of processing.

[0085] The exposure-map creating program 97 executed by the exposure-map
creating apparatus 40 has a module configuration including the units such
as the exposure-map creating unit 45. The units are loaded onto a main
storage and generated on the main storage.

[0086] The configuration of the exposure apparatus 60 is explained below.
FIG. 10 is a block diagram of the configuration of the exposure
apparatus. The exposure apparatus 60 is, for example, an exposure
apparatus of a step and scan system that synchronously scans a reticle
and a wafer with respect to a projection optical system to perform
exposure. The exposure apparatus 60 changes scan speed (moving speed) of
a reticle stage and a wafer stage to thereby control an exposure
distribution in a shot. The exposure apparatus 60 includes a control unit
61, an exposing mechanism 62, an exposure-map input unit 63, and an
exposure-map storing unit 64.

[0087] The exposure-map input unit 63 receives input of the exposure map
m3 from an external apparatus or the like. The exposure-map creating
apparatus 40 (the exposure determining apparatus) can be mounted on the
inside of the exposure apparatus 60. In this case, the exposure map m3 is
created on the inside of the exposure apparatus. The exposure-map storing
unit 64 is a memory or the like that stores the exposure map m3. The
control unit 61 has a function of controlling the exposing mechanism 62
using the exposure map m3 and includes a scan-speed control section 71, a
reticle-stage control section 72, and a wafer-stage control section 73.

[0088] The scan-speed control section 71 adjusts scan speed in a shot such
that the inside of the shot is exposed in an exposure distribution
corresponding to the exposure map m3. The reticle-stage control section
72 controls a moving direction or the like of the reticle stage. The
wafer-stage control section 73 controls a moving direction or the like of
the wafer stage.

[0089] The exposing mechanism 62 has a function of performing exposure
processing to a wafer according to an instruction from the control unit
61 and includes a reticle stage 81 and a wafer stage 82. A reticle (a
mask) is placed on the reticle stage 81. The reticle stage 81 moves the
reticle in an XY plane according to an instruction from the reticle-stage
control section 72. A wafer is placed on the wafer stage 82. The wafer
stage 82 moves the wafer in the XY plane according to an instruction from
the wafer-stage control section 73.

[0090] When the exposure apparatus 60 does not perform correction of an
exposure, the exposure apparatus 60 performs exposure in a state in which
predetermined speed is maintained in a position of an exposure area. At
this point, the reticle stage 81 and the wafer stage 82 are moved in a
synchronized state according to an instruction from the control unit 61
to move in directions opposite to each other.

[0091] When the exposure apparatus 60 performs the correction of an
exposure, the control unit 61 controls an exposure in a shot by changing
scan speed while maintaining a moving amount ratio and a ratio of scan
speeds of the reticle stage 81 and the wafer stage 82. Specifically, the
control unit 61 controls the scan speeds of the reticle stage 81 and the
wafer stage 82 to obtain an exposure distribution corresponding to the
exposure map m3.

[0092] In this embodiment, the exposure map m3 for correcting a deviation
amount between the pattern-on-wafer map m2 and a target pattern shape is
created. Therefore, it is possible to correct, with the exposure map m3,
a systematic dimension error in a shot on the wafer caused by the mask
manufacturing process P1 and the pattern forming process P2. It is
possible to correct, by performing the exposure processing using the
exposure map m3, dimension fluctuation on the wafer due to systematic
fluctuation in a mask surface and systematic fluctuation in optical
parameters in a shot during exposure. In other words, because a dimension
error caused by systematic fluctuation can be reduced by using the
exposure map m3, it is possible to relax specifications of systematic
fluctuation that can be allowed in the process units.

[0093] Therefore, it is possible to reduce dimension fluctuation on the
wafer due to systematic evaluation value fluctuation on the mask. As a
result, it is possible to substantially improve dimension uniformity on
the wafer. It is confirmed that, by using the exposing method according
to this embodiment, dimension accuracy in a shot is improved by
percentage as high as about 20% compared with the exposing method in the
past.

[0094] In the first and second embodiments, the optimum exposure
correction amount B is determined based on a pattern shape of a mask
pattern or a pattern on wafer. However, the optimum exposure correction
amount B can be determined based on a pattern dimension of the mask
pattern or the pattern on wafer. In this case, the pattern dimension of
the mask pattern is calculated by a mask manufacturing simulation using
the mask data D2 in advance. The pattern dimension of the pattern on
wafer is calculated by an optical simulation or a processing simulation
using the mask pattern shape D3 in advance.

[0095] According to the second embodiment, an exposure correction amount
or an exposure in a shot is determined based on a two-dimensional pattern
shape stored in the mask pattern map m1. Therefore, it is possible to
accurately determine an exposure correction amount or an exposure for
enabling formation of a pattern having a desired two-dimensional shape
parameter on the wafer.

[0096] A pattern dimension is calculated by the mask manufacturing
simulation, the optical simulation, or the processing simulation and the
optimum exposure correction amount B is determined based on the
calculated pattern dimension. Therefore, it is possible to accurately
determine an exposure correction amount for enabling formation of a
pattern having a desired dimension on the wafer.

[0097] While certain embodiments have been described, these embodiments
have been presented by way of example only, and are not intended to limit
the scope of the inventions. Indeed, the novel embodiments described
herein may be embodied in a variety of other forms; furthermore, various
omissions, substitutions and changes in the form of the embodiments
described herein may be made without departing from the spirit of the
inventions. The accompanying claims and their equivalents are intended to
cover such forms or modifications as would fall within the scope and
spirit of the inventions.